Colored coating and process for producing the same



Patented Apr. 12, 1932 PATENT OFFICE JOSEPH SCHULEIN, OF ROCKFORD, ILLINOIS COLORED COATING AND PROCESS FOR PRODUCING THE SAME No Drawing.

My invention relates to the art of producing colored coatings upon zinc or zinc coated surfaces by electrolytic means.

One object of this invention is toprovide colored coatings for zinc or zinc plated surfaces which will be more pleasing to the eye than the metallic color.

Another object is to provide colored coatings for zinc or zinc coated surfaces which Enay be easily and evenly applied to the surace.

Still another object is to provide colored metallic coatings for zinc or zinc coated surfaces in which the color will be permanent and relatively unaffected by light or atmospheric action and which Will not crack, chip or peel while being handled or while in use.

I have also aimed to provide colored metallic coatings for zinc or zinc coated surfaces which will have hi h resistance to corrosion and increase the li e of the metal.

A further object of my invention is to provide colored metallic coatings for zinc or zinc coated surfaces which will serve to hold paints to the surface of the metal.

My invention consists generally in a process for the treatment of zinc or zinc coated surfaces whereby a colored coating is formed u on the surface. Ihave found that when zinc or zinc coated articles are made either or both electrodes in a bath substantially similar to that used for chromium plating while an alternating current is caused to pass, a colored coating soon appears at the surface of the metal. If zinc articles to be treated are used as both electrodes, coating will occur on each article. On the other hand, if an'insoluble electrode such as platinum is used as either electrode and a zinc article used as the 40 other electrode, only the zinc will be coated in the manner contemplated. The theory of this formation is not known. Spectroscopic analysis shows the presence of chromium in the coating but this is throught to be only such amounts as are imprisoned or occluded. However, polychrome colors may be obtained upon galvanized iron by varying the solutions and current densities. This is aided by a short immersion in dilute sulphuric acid solution before treatment. The coating matetrolytic coatings are produced upon metals,

Application filed September 24, 1928. Serial No. 308,135.

rial appears to be very highly opaque since very thin films are sufficient to completely hide the natural color of the metal. This coatlng clings tenaciously to the surface, may not easily be'removed by rubbing, will not crack except as the metal itself cracks, will not peel or chip, and the coatings may be pollshed togive a bright glossy finish without apparent detrimental effect.

For example, two pieces of metal which are to be treated are cleaned in the common electrolytic cleaner and then immersed in the bath, each being made a terminal of the circuit in the bath. Thou h a large variety of solutions may be used l have found the 65 following to be well suited to my process: 250 grams OrO 3 grams Or (SO 1000 cubic 0. H O. While the process is operative at both high and low frequencies, 60 cycles seems to produce the best results. Increasing the frequency adds only slightly to the rate of formation while decreasing the frequency therefrom rapidly decreases the rate of formation. The voltage drop through the cell amounts to about 4 volts. The optimum temperature appears to be about 80 centigrade though this seems but slightly better than atmospheric temperatures. Excessively high temperatures (approaching the boiling point) decrease the rate of formation. A current density of about 1 ampere per square inch has been used very eflectively when about 3 minutes are required to produce an opaque coating.

I have also observed that a uniform coating is obtained under circumstances adverse to a plating process where, for example, the

electrode was placed behind a shield having a small opening in which case an apparently uniform coating resulted.

One of the features of the invention is the use of alternating current. In all other proc esses with which I am familiar where elecdirect current is essential. In my process alternating current is required and, while not definitely known, it is thought not to be an electro-deposition process in the common sense of the term. A result wholly new is obtained for the production of colored coatings.

1. A process for producing colored coat-v ings upon the surface of zinc comprising passing of alternating electric current through solutions containing chromium using the zinc to be treated as one electrode and an insoluble metal as the second.

2. A process for producing colored coatings upon the surface of zinc comprising passing of alternating electric current through solutions containing chromium using the zinc to be treated for both electrodes.

3. A process for producing colored coatings upon the surface of zinc comprising passing alternating electric current through a solution having substantially the properties of the following250 grams C10 3 grams Cr (SO 1000 cubic c. H O, using the zinc to be treated as electrodes.

4. As an article of manufacture, zinc surfaces having colored. metallic, electrolytic coatings formed by passing alternating electric current through solutions containing chromium using the metal to be treated for both electrodes.

5. A process for producing colored coating upon the surface of zinc comprising passing alternating electric current of frequency greater than 25 through a solution containing chromium and a sulphate ion using the metal to be treated as one electrode and an insoluble metal as the second.

6. A process for producing colored coating upon the surface of zinc comprising passing alternating electric current of frequency in the region of 60 through a solution containing chromium using the aim to be treated as one electrode and the insoluble metal as the second.

7. A process for producing colored coating upon the surface of zinc comprising passing alternating electric current of a frequency greater than 25 through a solution containing chromium and a sulphate ion, using the zinc to be treated for both electrodes.

8. A process for producing colored coating upon the surface of zinc comprising passing alternating electric current of frequency in the region of 60 through a solution containing chromium and a sulphate ion, using the zinc to be treated for both electrodes.

9. A process for producing colored coating upon the surface of zinc comprising passing alternating electric current of frequency greater than 25 through a solution having substantially the properties of the following:

250 grams CrO 3 grams Gr (SO 1000 cubic c. H O, using the zinc to be treated as nature.

JOSEPH SCHULEIN. 

